I am perplexed by the phrase in the Divine Mercy chaplet, "I offer you the body and blood, soul and divinity, of your dearly beloved Son, our Lord Jesus Christ, in atonement for our sins and those of the whole world." I thought that was something only a priest could do during the sacrifice of the Mass. Surely the offering made in the Mass is different in some way than what is offered in praying this chaplet. What am I missing?
Saying that prayer is not the same as offering Mass. At Mass we participate in the one sacrifice that Jesus made for us. But because he made that sacrifice, that perfect prayer is now ours. Therefore we can always make reference to it. It is a most powerful prayer because it is his prayer. Basically, what we are saying to the Father is: “By the merits of his Passion, we ask for your mercy!”